Over the last fifteen years or so there has been an increasing interest in complexes other than the Ziegler-Natta complexes which have the potential to polymerize olefins. The work of EXXON and Dow have lead to the commercialization of metallocene and constrained geometry catalysts which produce polymers tending to have a single active catalyst site. This type of research has lead to more complex ligand structures such as those of Brookhart which also show activity as polymerization catalysts. These systems are used with transition metals as the active catalyst center. There is a desire to find new species which may be capable of olefin polymerization with metals other than the transition metals.
There was a poster presentation by Christopher M. Ong and Professor Douglas W. Stephan of the University of Windsor at the summer meeting of the Chemical Institute of Canada in Toronto which disclosed aluminum phosphinimine complexes. The complex disclosed is a mono aluminum complex having phenyl substituents on the phosphorus atom and trimethyl silyl substituents on the nitrogen atom. The presentation does not disclose the dimer of the present invention.
Jordan et al. JACS 1997, 119, 8125 "Cationic Aluminum Alkyl Complexes Incorporating Amidinate Ligands", teaches amine, imine and aluminum complexes. The paper does not teach complexes of aluminum phosphinimine. The polymerization activity of the complexes of Jordan is very low.
Gibson et al. Chem. Commun. 1998, 2523 "Novel Aluminum Ethylene Polymerization Catalysts Based on Monoaonic N,N,N,-Pyridyliminoamide Ligands" teaches the polymerization of ethylene using a complex with a "Brookhart" tridentate ligand and aluminum. Gibson's catalyst does not teach the complexes of aluminum phosphinimine of the present invention. Further, the polymerization activity of the complexes of Gibson is very low.
The present invention seeks to provide novel aluminum complexes and processes for polymerizing olefins using such complexes.